U.S. patent application number 14/783697 was filed with the patent office on 2016-03-17 for method and apparatus for multilayer transmission and hybrid relaying with multiple out-of-band relays.
This patent application is currently assigned to NEW JERSEY INSTITUTE OF TECHNOLOGY. The applicant listed for this patent is INTERDIGITAL PATENT HOLDINGS, INC., NEW JERSEY INSTITUTE OF TECHNOLOGY. Invention is credited to Seok-Hwan PARK, Onur SAHIN, Osvaldo SIMEONE, Ariela ZEIRA.
Application Number | 20160080055 14/783697 |
Document ID | / |
Family ID | 48095691 |
Filed Date | 2016-03-17 |
United States Patent
Application |
20160080055 |
Kind Code |
A1 |
SAHIN; Onur ; et
al. |
March 17, 2016 |
METHOD AND APPARATUS FOR MULTILAYER TRANSMISSION AND HYBRID
RELAYING WITH MULTIPLE OUT-OF-BAND RELAYS
Abstract
A method and apparatus for hybrid multi-layer transmission
includes receiving a multi-layer signal from a source device,
wherein the multi-layer signal includes a plurality of sublayers. A
quantity of the plurality of sublayers is decoded and partial
information relating to the decoded sublayers is transmitted to a
destination device.
Inventors: |
SAHIN; Onur; (London,
GB) ; PARK; Seok-Hwan; (Millburn, NJ) ;
SIMEONE; Osvaldo; (New York City, NY) ; ZEIRA;
Ariela; (Huntington, NY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
INTERDIGITAL PATENT HOLDINGS, INC.
NEW JERSEY INSTITUTE OF TECHNOLOGY |
Wilmington
Newark |
DE
NJ |
US
US |
|
|
Assignee: |
NEW JERSEY INSTITUTE OF
TECHNOLOGY
Newark
NJ
INTERDIGITAL PATENT HOLDINGS, INC.
Wilmington
DE
|
Family ID: |
48095691 |
Appl. No.: |
14/783697 |
Filed: |
April 11, 2014 |
PCT Filed: |
April 11, 2014 |
PCT NO: |
PCT/US14/33729 |
371 Date: |
October 9, 2015 |
Current U.S.
Class: |
375/267 |
Current CPC
Class: |
C08K 5/42 20130101; H04W
88/08 20130101; C07D 307/12 20130101; C07D 307/24 20130101; C08K
5/1535 20130101; H04B 7/0473 20130101; H04B 7/155 20130101; C08K
5/11 20130101 |
International
Class: |
H04B 7/04 20060101
H04B007/04; H04W 88/08 20060101 H04W088/08; H04B 7/155 20060101
H04B007/155 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 12, 2013 |
EP |
13163577.3 |
Claims
1. A method for use in a relay performing hybrid multi-layer
transmission, comprising: receiving a multi-layer signal from a
source device, wherein the multi-layer signal includes a plurality
of sublayers; decoding a quantity of the plurality of sublayers;
and transmitting information relating to the decoded sublayers to a
destination device.
2. The method of claim 1, further comprising: compressing the
received multi-layer signal; and transmitting the compressed
multi-layer signal to the destination device.
3. The method of claim 2, further comprising generating a sequence
associated with the received multi-layer signal and transmitting a
compressed index associated with the sequence to the destination
device.
4. The method of claim 1 wherein the information includes a subset
of bits that comprise the decoded sublayers.
5. The method of claim 1 wherein the source device is an
encoder.
6. The method of claim 1 wherein the destination device is a
decoder.
7. A method for hybrid multi-layer transmission, implemented in a
base station, comprising: generating a plurality of sublayers from
a message for transmission; and transmitting the plurality of
sublayers to a plurality of relays, wherein each relay of the
plurality of relays decodes a subset of the plurality of sublayers
for transmission to a decoder.
8. The method of claim 7 wherein each of the sublayers include a
corresponding transmission rate for transmission to each of the
plurality of relays.
9. A relay, comprising: circuitry configured to receive a
multi-layer signal from a source device, wherein the multi-layer
signal includes a plurality of sublayers; circuitry configured to
decode a quantity of the plurality of sublayers; and circuitry
configured to transmit information relating to the decoded
sublayers to a destination device.
10. The relay of claim 9, further comprising: circuitry configured
to compress the received multi-layer signal; and circuitry
configured to transmit the compressed multi-layer signal to the
destination device.
11. The relay of claim 10, further comprising circuitry configured
to generate a sequence associated with the received multi-layer
signal and transmit a compressed index associated with the sequence
to the destination device.
12. The relay of claim 9 wherein the information includes a subset
of bits that comprise the decoded sublayers.
13. An encoder, comprising: circuitry configured to generate a
plurality of sublayers from a message for transmission; and
circuitry configured to transmit the plurality of sublayers to a
plurality of relays, wherein each relay of the plurality of relays
decodes a subset of the plurality of sublayers for transmission to
a decoder.
14. The encoder of claim 13 wherein each of the sublayers include a
corresponding transmission rate for transmission to each of the
plurality of relays.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Patent Application No. 61/811,404 filed Apr. 12, 2013, the contents
of which are hereby incorporated by reference herein.
BACKGROUND
[0002] Multiple relay networks, in which a source encoder
communicates with a destination device through a number of relays,
may be utilized for a wide range of applications. Activity in a
multiple relay network may focus on Gaussian networks in which a
first hop amounts to a Gaussian broadcast channel from a source
device to relays, and a second hop to a multiple access channel
between relays and receivers. Various transmission strategies,
including decode-and-forward (DF), compress-and-forward (CF),
amplify-and-forward (AF) and hybrid AF-DF, may be utilized for
communication in such a network.
[0003] In a variation of a classical multi-relay channel, relays
may be connected to the destination through digital backhaul links
of finite-capacity. For example, this model may be utilized in
cloud radio cellular networks, in which the base stations (BSs) may
act as relays connected to the central decoder via finite-capacity
backhaul links.
[0004] Pooling multiple relays into a distributed multiple-input
multiple-output (MIMO) system includes a number of issues that may
need to be addressed. High-performance operation of such systems
may require a centralized data and channel processor, which may
place significant throughput and latency requirements on the
backhaul links which connect the relays to the centralized
processor. For example, in cloud radio cellular networks, where
base stations act as relays connected to the central decoder in the
cloud, the backhaul problem may be acute because the links may have
a finite capacity that may be insufficient for traditional
approaches.
SUMMARY
[0005] A method and apparatus for hybrid multi-layer transmission
is disclosed. The method includes receiving a multi-layer signal
from a source device, wherein the multi-layer signal includes a
plurality of sublayers. A quantity of the plurality of sublayers is
decoded and partial information relating to the decoded sublayers
is transmitted to a destination device.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] A more detailed understanding may be had from the following
description, given by way of example in conjunction with the
accompanying drawings wherein:
[0007] FIG. 1A is a system diagram of an example communications
system in which one or more disclosed embodiments may be
implemented;
[0008] FIG. 1B is a system diagram of an example wireless
transmit/receive unit (WTRU) that may be used within the
communications system illustrated in FIG. 1A;
[0009] FIG. 1C is a system diagram of an example radio access
network and an example core network that may be used within the
communications system illustrated in FIG. 1A;
[0010] FIG. 2 is an example system diagram of a network including
multiple relays in communication with and encoder and a decoder via
out-of-band digital backhaul links within given capacities;
[0011] FIG. 3 is a flow diagram of an example method of multilayer
transmission with hybrid relaying;
[0012] FIG. 4 is an example diagram depicting achievable rates
versus the backhaul capacity C.sub.1=C.sub.2 in a symmetric network
with M=2, P=0 dB, and g.sub.1=g.sub.2=10 dB ; and
[0013] FIG. 5 is an example diagram depicting achievable rates
versus the back haul capacity C.sub.1=C.sub.2 per relay with M=2,
P=0 dB, and [g.sub.1, g.sub.2]=[0,10 ]dB.
DETAILED DESCRIPTION
[0014] FIG. 1A is a diagram of an example communications system 100
in which one or more disclosed embodiments may be implemented. The
communications system 100 may be a multiple access system that
provides content, such as voice, data, video, messaging, broadcast,
etc., to multiple wireless users. The communications system 100 may
enable multiple wireless users to access such content through the
sharing of system resources, including wireless bandwidth. For
example, the communications systems 100 may employ one or more
channel access methods, such as code division multiple access
(CDMA), time division multiple access (TDMA), frequency division
multiple access (FDMA), orthogonal FDMA (OFDMA), single-carrier
FDMA (SC-FDMA), and the like.
[0015] As shown in FIG. 1A, the communications system 100 may
include wireless transmit/receive units (WTRUs) 102a, 102b, 102c,
102d, a radio access network (RAN) 104, a core network 106, a
public switched telephone network (PSTN) 108, the Internet 110, and
other networks 112, though it will be appreciated that the
disclosed embodiments contemplate any number of WTRUs, base
stations, networks, and/or network elements. Each of the WTRUs
102a, 102b, 102c, 102d may be any type of device configured to
operate and/or communicate in a wireless environment. By way of
example, the WTRUs 102a, 102b, 102c, 102d may be configured to
transmit and/or receive wireless signals and may include user
equipment (UE), a mobile station, a fixed or mobile subscriber
unit, a pager, a cellular telephone, a personal digital assistant
(PDA), a smartphone, a laptop, a netbook, a personal computer, a
wireless sensor, consumer electronics, and the like.
[0016] The communications systems 100 may also include a base
station 114a and a base station 114b. Each of the base stations
114a, 114b may be any type of device configured to wirelessly
interface with at least one of the WTRUs 102a, 102b, 102c, 102d to
facilitate access to one or more communication networks, such as
the core network 106, the Internet 110, and/or the other networks
112. By way of example, the base stations 114a, 114b may be a base
transceiver station (BTS), a Node-B, an eNode B, a Home Node B, a
Home eNode B, a site controller, an access point (AP), a wireless
router, and the like. While the base stations 114a, 114b are each
depicted as a single element, it will be appreciated that the base
stations 114a, 114b may include any number of interconnected base
stations and/or network elements.
[0017] The base station 114a may be part of the RAN 104, which may
also include other base stations and/or network elements (not
shown), such as a base station controller (BSC), a radio network
controller (RNC), relay nodes, etc. The base station 114a and/or
the base station 114b may be configured to transmit and/or receive
wireless signals within a particular geographic region, which may
be referred to as a cell (not shown). The cell may further be
divided into cell sectors. For example, the cell associated with
the base station 114a may be divided into three sectors. Thus, in
one embodiment, the base station 114a may include three
transceivers, i.e., one for each sector of the cell. In another
embodiment, the base station 114a may employ multiple-input
multiple-output (MIMO) technology and, therefore, may utilize
multiple transceivers for each sector of the cell.
[0018] The base stations 114a, 114b may communicate with one or
more of the WTRUs 102a, 102b, 102c, 102d over an air interface 116,
which may be any suitable wireless communication link (e.g., radio
frequency (RF), microwave, infrared (IR), ultraviolet (UV), visible
light, etc.). The air interface 116 may be established using any
suitable radio access technology (RAT).
[0019] More specifically, as noted above, the communications system
100 may be a multiple access system and may employ one or more
channel access schemes, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA,
and the like. For example, the base station 114a in the RAN 104 and
the WTRUs 102a, 102b, 102c may implement a radio technology such as
Universal Mobile Telecommunications System (UMTS) Terrestrial Radio
Access (UTRA), which may establish the air interface 116 using
wideband CDMA (WCDMA). WCDMA may include communication protocols
such as High-Speed Packet Access (HSPA) and/or Evolved HSPA
(HSPA+). HSPA may include High-Speed Downlink Packet Access (HSDPA)
and/or High-Speed Uplink Packet Access (HSUPA).
[0020] In another embodiment, the base station 114a and the WTRUs
102a, 102b, 102c may implement a radio technology such as Evolved
UMTS Terrestrial Radio Access (E-UTRA), which may establish the air
interface 116 using Long Term Evolution (LTE) and/or LTE-Advanced
(LTE-A).
[0021] In other embodiments, the base station 114a and the WTRUs
102a, 102b, 102c may implement radio technologies such as IEEE
802.16 (i.e., Worldwide Interoperability for Microwave Access
(WiMAX)), CDMA2000, CDMA2000 1X, CDMA2000 EV-DO, Interim Standard
2000 (IS-2000), Interim Standard 95 (IS-95), Interim Standard 856
(IS-856), Global System for Mobile communications (GSM), Enhanced
Data rates for GSM Evolution (EDGE), GSM EDGE (GERAN), and the
like.
[0022] The base station 114b in FIG. 1A may be a wireless router,
Home Node B, Home eNode B, or access point, for example, and may
utilize any suitable RAT for facilitating wireless connectivity in
a localized area, such as a place of business, a home, a vehicle, a
campus, and the like. In one embodiment, the base station 114b and
the WTRUs 102c, 102d may implement a radio technology such as IEEE
802.11 to establish a wireless local area network (WLAN). In
another embodiment, the base station 114b and the WTRUs 102c, 102d
may implement a radio technology such as IEEE 802.15 to establish a
wireless personal area network (WPAN). In yet another embodiment,
the base station 114b and the WTRUs 102c, 102d may utilize a
cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE, LTE-A, etc.)
to establish a picocell or femtocell. As shown in FIG. 1A, the base
station 114b may have a direct connection to the Internet 110.
Thus, the base station 114b may not be required to access the
Internet 110 via the core network 106.
[0023] The RAN 104 may be in communication with the core network
106, which may be any type of network configured to provide voice,
data, applications, and/or voice over internet protocol (VoIP)
services to one or more of the WTRUs 102a, 102b, 102c, 102d. For
example, the core network 106 may provide call control, billing
services, mobile location-based services, pre-paid calling,
Internet connectivity, video distribution, etc., and/or perform
high-level security functions, such as user authentication.
Although not shown in FIG. 1A, it will be appreciated that the RAN
104 and/or the core network 106 may be in direct or indirect
communication with other RANs that employ the same RAT as the RAN
104 or a different RAT. For example, in addition to being connected
to the RAN 104, which may be utilizing an E-UTRA radio technology,
the core network 106 may also be in communication with another RAN
(not shown) employing a GSM radio technology.
[0024] The core network 106 may also serve as a gateway for the
WTRUs 102a, 102b, 102c, 102d to access the PSTN 108, the Internet
110, and/or other networks 112. The PSTN 108 may include
circuit-switched telephone networks that provide plain old
telephone service (POTS). The Internet 110 may include a global
system of interconnected computer networks and devices that use
common communication protocols, such as the transmission control
protocol (TCP), user datagram protocol (UDP) and the internet
protocol (IP) in the TCP/IP internet protocol suite. The networks
112 may include wired or wireless communications networks owned
and/or operated by other service providers. For example, the
networks 112 may include another core network connected to one or
more RANs, which may employ the same RAT as the RAN 104 or a
different RAT.
[0025] Some or all of the WTRUs 102a, 102b, 102c, 102d in the
communications system 100 may include multi-mode capabilities,
i.e., the WTRUs 102a, 102b, 102c, 102d may include multiple
transceivers for communicating with different wireless networks
over different wireless links. For example, the WTRU 102c shown in
FIG. 1A may be configured to communicate with the base station
114a, which may employ a cellular-based radio technology, and with
the base station 114b, which may employ an IEEE 802 radio
technology.
[0026] FIG. 1B is a system diagram of an example WTRU 102. As shown
in FIG. 1B, the WTRU 102 may include a processor 118, a transceiver
120, a transmit/receive element 122, a speaker/microphone 124, a
keypad 126, a display/touchpad 128, non-removable memory 130,
removable memory 132, a power source 134, a global positioning
system (GPS) chipset 136, and other peripherals 138. It will be
appreciated that the WTRU 102 may include any sub-combination of
the foregoing elements while remaining consistent with an
embodiment.
[0027] The processor 118 may be a general purpose processor, a
special purpose processor, a conventional processor, a digital
signal processor (DSP), a plurality of microprocessors, one or more
microprocessors in association with a DSP core, a controller, a
microcontroller, Application Specific Integrated Circuits (ASICs),
Field Programmable Gate Array (FPGAs) circuits, any other type of
integrated circuit (IC), a state machine, and the like. The
processor 118 may perform signal coding, data processing, power
control, input/output processing, and/or any other functionality
that enables the WTRU 102 to operate in a wireless environment. The
processor 118 may be coupled to the transceiver 120, which may be
coupled to the transmit/receive element 122. While FIG. 1B depicts
the processor 118 and the transceiver 120 as separate components,
it will be appreciated that the processor 118 and the transceiver
120 may be integrated together in an electronic package or
chip.
[0028] The transmit/receive element 122 may be configured to
transmit signals to, or receive signals from, a base station (e.g.,
the base station 114a) over the air interface 116. For example, in
one embodiment, the transmit/receive element 122 may be an antenna
configured to transmit and/or receive RF signals. In another
embodiment, the transmit/receive element 122 may be an
emitter/detector configured to transmit and/or receive IR, UV, or
visible light signals, for example. In yet another embodiment, the
transmit/receive element 122 may be configured to transmit and
receive both RF and light signals. It will be appreciated that the
transmit/receive element 122 may be configured to transmit and/or
receive any combination of wireless signals.
[0029] In addition, although the transmit/receive element 122 is
depicted in FIG. 1B as a single element, the WTRU 102 may include
any number of transmit/receive elements 122. More specifically, the
WTRU 102 may employ MIMO technology. Thus, in one embodiment, the
WTRU 102 may include two or more transmit/receive elements 122
(e.g., multiple antennas) for transmitting and receiving wireless
signals over the air interface 116.
[0030] The transceiver 120 may be configured to modulate the
signals that are to be transmitted by the transmit/receive element
122 and to demodulate the signals that are received by the
transmit/receive element 122. As noted above, the WTRU 102 may have
multi-mode capabilities. Thus, the transceiver 120 may include
multiple transceivers for enabling the WTRU 102 to communicate via
multiple RATs, such as UTRA and IEEE 802.11, for example.
[0031] The processor 118 of the WTRU 102 may be coupled to, and may
receive user input data from, the speaker/microphone 124, the
keypad 126, and/or the display/touchpad 128 (e.g., a liquid crystal
display (LCD) display unit or organic light-emitting diode (OLED)
display unit). The processor 118 may also output user data to the
speaker/microphone 124, the keypad 126, and/or the display/touchpad
128. In addition, the processor 118 may access information from,
and store data in, any type of suitable memory, such as the
non-removable memory 130 and/or the removable memory 132. The
non-removable memory 130 may include random-access memory (RAM),
read-only memory (ROM), a hard disk, or any other type of memory
storage device. The removable memory 132 may include a subscriber
identity module (SIM) card, a memory stick, a secure digital (SD)
memory card, and the like. In other embodiments, the processor 118
may access information from, and store data in, memory that is not
physically located on the WTRU 102, such as on a server or a home
computer (not shown).
[0032] The processor 118 may receive power from the power source
134, and may be configured to distribute and/or control the power
to the other components in the WTRU 102. The power source 134 may
be any suitable device for powering the WTRU 102. For example, the
power source 134 may include one or more dry cell batteries (e.g.,
nickel-cadmium (NiCd), nickel-zinc (NiZn), nickel metal hydride
(NiMH), lithium-ion (Li-ion), etc.), solar cells, fuel cells, and
the like.
[0033] The processor 118 may also be coupled to the GPS chipset
136, which may be configured to provide location information (e.g.,
longitude and latitude) regarding the current location of the WTRU
102. In addition to, or in lieu of, the information from the GPS
chipset 136, the WTRU 102 may receive location information over the
air interface 116 from a base station (e.g., base stations 114a,
114b) and/or determine its location based on the timing of the
signals being received from two or more nearby base stations. It
will be appreciated that the WTRU 102 may acquire location
information by way of any suitable location-determination method
while remaining consistent with an embodiment.
[0034] The processor 118 may further be coupled to other
peripherals 138, which may include one or more software and/or
hardware modules that provide additional features, functionality
and/or wired or wireless connectivity. For example, the peripherals
138 may include an accelerometer, an e-compass, a satellite
transceiver, a digital camera (for photographs or video), a
universal serial bus (USB) port, a vibration device, a television
transceiver, a hands free headset, a Bluetooth.RTM. module, a
frequency modulated (FM) radio unit, a digital music player, a
media player, a video game player module, an Internet browser, and
the like.
[0035] FIG. 1C is a system diagram of the RAN 104 and the core
network 106 according to an embodiment. As noted above, the RAN 104
may employ a UTRA radio technology to communicate with the WTRUs
102a, 102b, 102c over the air interface 116. The RAN 104 may also
be in communication with the core network 106. As shown in FIG. 1C,
the RAN 104 may include Node-Bs 140a, 140b, 140c, which may each
include one or more transceivers for communicating with the WTRUs
102a, 102b, 102c over the air interface 116. The Node-Bs 140a,
140b, 140c may each be associated with a particular cell (not
shown) within the RAN 104. The RAN 104 may also include RNCs 142a,
142b. It will be appreciated that the RAN 104 may include any
number of Node-Bs and RNCs while remaining consistent with an
embodiment.
[0036] As shown in FIG. 1C, the Node-Bs 140a, 140b may be in
communication with the RNC 142a. Additionally, the Node-B 140c may
be in communication with the RNC 142b. The Node-Bs 140a, 140b, 140c
may communicate with the respective RNCs 142a, 142b via an Iub
interface. The RNCs 142a, 142b may be in communication with one
another via an Iur interface. Each of the RNCs 142a, 142b may be
configured to control the respective Node-Bs 140a, 140b, 140c to
which it is connected. In addition, each of the RNCs 142a, 142b may
be configured to carry out or support other functionality, such as
outer loop power control, load control, admission control, packet
scheduling, handover control, macrodiversity, security functions,
data encryption, and the like.
[0037] The core network 106 shown in FIG. 1C may include a media
gateway (MGW) 144, a mobile switching center (MSC) 146, a serving
GPRS support node (SGSN) 148, and/or a gateway GPRS support node
(GGSN) 150. While each of the foregoing elements are depicted as
part of the core network 106, it will be appreciated that any one
of these elements may be owned and/or operated by an entity other
than the core network operator.
[0038] The RNC 142a in the RAN 104 may be connected to the MSC 146
in the core network 106 via an IuCS interface. The MSC 146 may be
connected to the MGW 144. The MSC 146 and the MGW 144 may provide
the WTRUs 102a, 102b, 102c with access to circuit-switched
networks, such as the PSTN 108, to facilitate communications
between the WTRUs 102a, 102b, 102c and traditional land-line
communications devices.
[0039] The RNC 142a in the RAN 104 may also be connected to the
SGSN 148 in the core network 106 via an IuPS interface. The SGSN
148 may be connected to the GGSN 150. The SGSN 148 and the GGSN 150
may provide the WTRUs 102a, 102b, 102c with access to
packet-switched networks, such as the Internet 110, to facilitate
communications between and the WTRUs 102a, 102b, 102c and
IP-enabled devices.
[0040] As noted above, the core network 106 may also be connected
to the networks 112, which may include other wired or wireless
networks that are owned and/or operated by other service
providers.
[0041] As described in more detail below, a communication network
may include a transmitter, (e.g., source/encoder), communicating
with a receiver, (e.g., destination/decoder), through a number of
out-of-band relays that are connected to the decoder through
capacity-constrained digital backhaul links. A transmission and
relaying strategy in which multi-layer transmission is used may
leverage different decoding capabilities of the relays to enable
hybrid DF and CF relaying. Each relay may forward part of a decoded
message and a compressed version of the received signal. Utilizing
a multi-layer strategy may facilitate decoding at the destination
based on the information received from the relays. In an alternate
broadcast coding approach, each layer may encode an independent
message. As described below, each layer may encode a selected set
of independent messages.
[0042] FIG. 2 is an example system diagram of a network 200
including multiple relays in communication with an encoder and a
decoder via out-of-band digital backhaul links within given
capacities. As shown in the system 200 of FIG. 2, an encoder 210
communicates transmissions h (designated h.sub.1, h.sub.i, and
h.sub.M) to respective relays 220 (designated 220.sub.1, 220.sub.i,
and 220.sub.M), which transmit a respective communication along
backhaul links having capacity C (designated C.sub.1, C.sub.i, and
C.sub.M) to a decoder 230. FIG. 2 shows an example communication
with the multiple relays 220 connected to the decoder 230 via
out-of-band digital backhaul links within given capacities. In the
example network 200, h.sub.1= {square root over
(g.sub.1e.sup.j.theta..sup.1)}, h.sub.i= {square root over
(g.sub.ie.sup.j.theta..sup.i)}, and h.sub.M= {square root over
(g.sub.Me.sup.j.theta..sup.M)}. For purposes of example, either the
encoder 210, the decoder 230, or both, may be included in a base
station.
[0043] Accordingly, the network 200 depicts a variation of a
multi-relay channel discussed, in which the relays 220 are
connected to the destination, (i.e., decoder 230), through digital
backhaul links of finite-capacity. One motivation for this model
may come in the form of cloud radio cellular networks, in which the
base stations may act as relays connected to a central decoder via
the finite-capacity backhaul links.
[0044] A transmission strategy that is based on multi-layer
transmission and hybrid relaying may be utilized as described
below. Hybrid relaying may be performed by having each relay 220
forward part of the decoded messages, which may amount to partial
decode-and-forward (DF), along with a compressed version of the
received signal, thus adhering also to the compress-and-forward
(CF) paradigm. The multi-layer strategy used at the source may be
designed so as to facilitate decoding at the destination based on
the information received from the relays.
[0045] The amount of information decodable at the relays 220 may
depend on the generally different fading powers, (e.g., g.sub.1 . .
. , g.sub.M). To leverage the different channel qualities, flexible
decoding at the relays 220 may be enabled by adopting a multi-layer
transmission strategy at the encoder 210. For example, the
transmitter, (i.e., encoder 210), splits its message into
independent submessages or sublayers, (e.g., W.sub.1, . . . ,
W.sub.M+1), with corresponding rates R.sub.1, . . . , R.sub.M+1 in
bit(s) per channel use (bit/c.u.), respectively. The idea is that
message W.sub.1 may be decoded by all relays 220, message W.sub.2
only by relays 2, . . . , M, (i.e., 220.sub.2 . . . 220.sub.M), and
so on. This way, relays 220 having better channel conditions may
decode more information. Additionally, message W.sub.M+1 may be
instead decoded only at the destination, (i.e., decoder 230).
[0046] To encode these messages, the encoded signal may be given
by
X = k = 1 M + 1 P k X k , Equation 1 ##EQU00001##
where the signals X.sub.1, . . . , X.sub.M+1 are independent and
distributed as XN(0,1), and the power coefficients P.sub.1, . . . ,
P.sub.M+1 are subject to the power constraint
.SIGMA..sub.k=1.sup.M+1P.sub.k.ltoreq.P. The signal X.sub.1 may
encode message W.sub.1, signal X.sub.2 may encode both messages
W.sub.1 and W.sub.2, and so on. Accordingly, signal X.sub.k may
encode messages W.sub.1, . . . , W.sub.k for k=1, . . . , M. Signal
X.sub.k may not only encode message W.sub.k, and signal X.sub.M+1
may encode message W.sub.M+1.
[0047] Therefore, Relay 1, (i.e., 220.sub.1), may decode message
W.sub.1 from X.sub.1, while relay 2, (i.e., 220.sub.2), may first
decode message W.sub.1 from X.sub.1, and then message W.sub.2 from
X.sub.2 using its knowledge of W.sub.1 and so on. Accordingly,
relay k may decode messages W.sub.1, . . . , W.sub.k for k=1, . . .
, M. From standard information-theoretic considerations, the
following conditions may be sufficient to guarantee that rates
R.sub.k are decodable by the relays
R.sub.k.ltoreq.I(X.sub.k; Y.sub.k|X.sub.1, . . . , X.sub.k-1),
Equation 2
for k=1, . . . , M. This may be because, in accordance with
Equations 1 and 2, with k=1, namely R.sub.1.ltoreq.I(X.sub.1;
Y.sub.1), may ensure that not only relay 1, but all relays may
decode message W.sub.1. Generalizing, the inequality for a given k
may guarantee that not only relay k may decode message W.sub.k
after having decoded W.sub.1, . . . , W.sub.k 1, but also all
relays k+1, . . . , M may decode message W.sub.k. The signal
X.sub.M+1, and thus message W.sub.M+1 may be decoded by the
destination, (i.e., decoder 230), only.
[0048] As discussed above, relay i, (i.e., 220.sub.i), may decode
messages W.sub.1, . . . , W.sub.i. Accordingly, each ith relay 220
may transmit partial information about the decoded messages to the
destination decoder 230 via the backhaul links. In other words,
each relay 220 may transmit specific subsets of the bits that make
up the decoded messages. The rate at which this partial information
may be transmitted to the destination decoder 230 may be selected
so as to enable the decoder 230 to decode messages W.sub.1, . . . ,
W.sub.M jointly based on all the signals received from the relays
220. C.sub.i.sup.DF.ltoreq.C.sub.i may be denoted as the portion of
the backhaul capacity devoted to the transmission of the messages
decoded by relay i.
[0049] Beside the rate allocated to the transmission of each part
of the decoded messages, relay i may utilize the residual backhaul
link to transmit a compressed version .sub.i of the received signal
Y.sub.i. The compression strategy at relay i may be characterized
by the test channel p(y.sub.i|y.sub.i) according to conventional
rate-distortion theory. Moreover, since the received signals at
different relays 220 may be correlated with each other, a
distributed source coding strategy may be utilized. Successive
decoding may be used via, for example, Wyner-Ziv compression, with
a given order .sub.n(1).fwdarw. . . . .fwdarw. .sub.n(M), where
.pi.(i) may be a given permutation of the relays 220 indices M.
Thus, the decoder 230 may successfully retrieve the descriptions)
.sub.1, . . . , .sub.M if the conditions
I(Y.sub..pi.(i); .sub..pi.(i)| .sub.{.pi.(1), . . . ,
.pi.(i-1)}).ltoreq.C.sub..pi.(i).sup.CF Equation 3
are satisfied for all i=1, . . . , M, where
C.sub.i.sup.CF.ltoreq.C.sub.i may be defined as the capacity
allocated by relay i to communicate the compressed received signal
.sub.i to the decoder 230. It may be recalled that Equation 3 is
the rate needed to compress Y.sub..pi.(i) as .sub..pi.(i) given
that the destination has side information given by the previously
decompressed signals .sub..pi.(1), . . . , .sub..pi.(i-1).
[0050] A Gaussian test channel p(y.sub.i|y.sub.i), may be utilized
so that the compressed signal .sub.i may be expressed as:
.sub.i=Y.sub.i+Q.sub.i, Equation 4
where the compression noise Q.sub.i: XN (0, .sigma..sub.i.sup.2))
may be independent of the received signal Y.sub.i to be
compressed.
[0051] The destination decoder 230 may first recover the
descriptions .sub.i, . . . , .sub.M from the signals received by
the relays 220. This step may be dependent that the conditions in
Equation 3 are satisfied. Having obtained .sub.M={ .sub.1, . . . ,
.sub.M}, the destination, (i.e., decoder 230), may jointly decode
the messages W.sub.1, . . . , W.sub.M based on the partial
information about these messages received from the relays 220 and
on the compressed received signals .sub.M. Finally, message
W.sub.M+1 may be decoded.
[0052] FIG. 3 is a flow diagram of an example method 300 of
multilayer transmission with hybrid relaying. FIG. 3 is an example
of a hybrid DF-CF relaying.
[0053] In step 310, the channel state is acquired. For example,
relay 220.sub.i, (relay i), may estimate channel h.sub.i for i=1, .
. . , M. The relay i may report its channel hi to the decoder 230
for i=1, . . . , M.
[0054] Transmission and compression strategies may be determined in
step 320. For example, the decoder 230 may compute power
allocations P.sub.1, . . . , P.sub.M+1, compression strategies
.beta..sub.1, . . . , .beta..sub.M, and the ordering .pi. for
decompression as described above. The decoder 230 may inform the
encoder 210 about the obtained power allocations P.sub.1, . . . ,
P.sub.M+1. Additionally, the decoder 230 may inform relay 220,
(relay i), about the obtained compression strategy .beta..sub.i for
i=1, . . . , M. The rate R.sub.k and corresponding modulation and
coding strategy ENC.sub.k to be used for layer k for k=1, . . . ,
M+1 may be computed by the decoder 230 and it may inform the
encoder 210 and relay 220.sub.i, (relay i) about the rate R.sub.i
and coding strategy ENC.sub.i for i=1, . . . , M, as well as
informing the encoder 210 about the rate R.sub.M+1 and coding
strategy ENC.sub.M+1.
[0055] In step 330, the encoder 210 transmits communications to the
relays 220. For example, the encoder 210, for a message
W.sub.k1.di-elect cons.{1, . . . , 2.sup.nR.sup.k} for k=1, . . . ,
M+1, may build codewords
{X.sub.k,t}.sub.t=1.sup.n=ENC.sub.k(W.sub.1, . . . , W.sub.k) for
k=1, . . . , M and
{X.sub.M+1,t}.sub.t=1.sup.n=ENC.sub.M+1(W.sub.M+1). The encoder 210
may transmit the signal
X t = k = 1 M + 1 P k X k , t ##EQU00002##
in channel use for t=1, . . . , n. Relay 220.sub.i, (relay i) may
receive signal Y.sub.i,t=h.sub.iX.sub.t+Z.sub.t for t=1, . . . ,
n.
[0056] In step 340, the relays 220 decode the communications,
generate sequences and transmit information to the decoder 230. For
example, Relay 220.sub.i, (relay i) may decode messages W.sub.1, .
. . , W.sub.i based on the sequence {Y.sub.i,t}.sub.t=1.sup.n for
i=1, . . . , M, and may generate the sequence {
.sub.i,t}.sub.t=1.sup.n with each signal .sub.i,t obtained by
quantizing Y.sub.i,t with noise Q.sub.i,t.about.CN(0,
.beta..sub.i.sup.-1-1), for example, .sub.i,t=Y.sub.i,t+Q.sub.i,t
for i=1, . . . , M. Relay 220.sub.i, (relay i) may also transmit
partial information about the decoded messages W.sub.1, . . . ,
W.sub.i and the index associated with the sequence {
.sub.i,t}.sub.t=1.sup.n to the decoder 230 via backhaul link of
capacity C.sub.i for i=1, . . . , M.
[0057] In step 350, the decoder 230 performs decompression and
decoding, the decoder 230 may first recover the signals for {
.sub.i,t}.sub.t=1.sup.n for i=1, . . . , M with the ordering {
.sub.i,t}.sub.t=1.sup.n.fwdarw. . . . .fwdarw.{
.sub..pi.(M),t}.sub.t=1.sup.n based on the indices collected from
the relays 220. The decoder 230 may decode jointly the message
W.sub.1, . . . , W.sub.M based on the partial information received
from the relays 220 and on the compressed signals {
.sub.i,t}.sub.t=1.sup.n for i=1, . . . , M. Finally, the decoder
230 may decode the message W.sub.M+1 based on the signals {
.sub.i,t}.sub.t=1.sup.n for i=1, . . . , M and the decoded messages
W.sub.1, . . . , W.sub.M.
[0058] Below are examples of numerical results of a multi-layer
transmission scheme with hybrid relaying described above as
compared to conventional schemes. For reference, achievable rates
may also be compared with the cutset upper bound
R cutset = min { 1 , , M } { j .di-elect cons. C j + log ( 1 + P j
.di-elect cons. c g j ) } . Equation 5 ##EQU00003##
[0059] For purposes of example, the case with two relays may be
focused on, for example, M=2. Single-layer schemes may be marked
with the label `SL` and multi-layer schemes with `ML`. For CF
related schemes, the optimal ordering .pi..sup.opt may be found via
exhaustive search and may be observed to be .pi.=(1,2) for all the
simulated cases.
[0060] FIG. 4 is an example diagram 400 depicting achievable rates
versus the backhaul capacity C.sub.1=C.sub.2 in a symmetric network
with M=2, P=0 dB, and g.sub.1=g.sub.2=10 dB. As shown in FIG. 4,
the performance in a symmetric setting may be examined by plotting
the rate versus the backhaul capacities C.sub.1=C.sub.2 when P=0 dB
and g.sub.1=g.sub.2=10 dB. In this symmetric set-up, the optimized
hybrid scheme may end up reducing to either the DF or the CF
strategy at small and large backhaul capacity, respectively. The
single-layer and multi-layer strategies may not be distinguishable
since they show the same performance when the relays experience the
same fading power, for example, g.sub.1=g.sub.2. This may be a
result of multi-layer strategies being relevant only when two
relays have different decoding capabilities.
[0061] FIG. 5 is an example diagram 500 depicting achievable rates
versus the back haul capacity C.sub.1=C.sub.2 per relay with M=2,
P=0 dB, and [g.sub.1, g.sub.2]=[0,10] dB. As shown in FIG. 5, the
performance may be observed versus the backhaul C.sub.1=C.sub.2
with P=0 dB and asymmetric channel powers [g.sub.1, g.sub.2]=[0,10]
dB. Unlike the symmetric setting in FIG. 4, the multi-layer
strategy may be beneficial compared to the single-layer (SL)
transmission for both DF and Hybrid schemes. Moreover, unlike the
setting of FIG. 4, the hybrid relaying strategy may show a
performance advantage with respect to all other schemes. This may
be the case for intermediate values of the backhaul capacities
C.sub.1=C.sub.2. It may also be mentioned that, as C.sub.1=C.sub.2
increases, the performance of DF schemes may be limited by the
capacity of the better decoder, namely log.sub.2(1+10)=3.46
bit/c.u., while CF, and thus also the hybrid strategy, are able,
for C.sub.1=C.sub.2 large enough, to achieve the cutset bound.
[0062] Although features and elements are described above in
particular combinations, one of ordinary skill in the art will
appreciate that each feature or element can be used alone or in any
combination with the other features and elements. In addition, the
methods described herein may be implemented in a computer program,
software, or firmware incorporated in a computer-readable medium
for execution by a computer or processor. Examples of
computer-readable media include electronic signals (transmitted
over wired or wireless connections) and computer-readable storage
media. Examples of computer-readable storage media include, but are
not limited to, a read only memory (ROM), a random access memory
(RAM), a register, cache memory, semiconductor memory devices,
magnetic media such as internal hard disks and removable disks,
magneto-optical media, and optical media such as CD-ROM disks, and
digital versatile disks (DVDs). A processor in association with
software may be used to implement a radio frequency transceiver for
use in a WTRU, UE, terminal, base station, RNC, or any host
computer.
* * * * *